netdev - Re: [PATCH net-next v2] tcp: Dump bound-only sockets in inet

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Date: Tue, 28 Nov 2023 02:13:42 +0100
From: Guillaume Nault <gnault@...hat.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com,
	kuba@...nel.org, mkubecek@...e.cz, netdev@...r.kernel.org,
	pabeni@...hat.com
Subject: Re: [PATCH net-next v2] tcp: Dump bound-only sockets in inet_diag.

On Mon, Nov 27, 2023 at 09:56:43AM -0800, Kuniyuki Iwashima wrote:
> From: Guillaume Nault <gnault@...hat.com>
> Date: Mon, 27 Nov 2023 18:26:05 +0100
> > On Fri, Nov 24, 2023 at 05:39:42PM -0800, Kuniyuki Iwashima wrote:
> > > > +			spin_lock_bh(&ibb->lock);
> > > > +			inet_bind_bucket_for_each(tb2, &ibb->chain) {
> > > > +				if (!net_eq(ib2_net(tb2), net))
> > > > +					continue;
> > > > +
> > > > +				sk_for_each_bound_bhash2(sk, &tb2->owners) {
> > > > +					struct inet_sock *inet = inet_sk(sk);
> > > > +
> > > > +					if (num < s_num)
> > > > +						goto next_bind;
> > > > +
> > > > +					if (sk->sk_state != TCP_CLOSE ||
> > > > +					    !inet->inet_num)
> > > > +						goto next_bind;
> > > > +
> > > > +					if (r->sdiag_family != AF_UNSPEC &&
> > > > +					    r->sdiag_family != sk->sk_family)
> > > > +						goto next_bind;
> > > > +
> > > > +					if (!inet_diag_bc_sk(bc, sk))
> > > > +						goto next_bind;
> > > > +
> > > > +					if (!refcount_inc_not_zero(&sk->sk_refcnt))
> > > > +						goto next_bind;
> > > 
> > > I guess this is copied from the ehash code below, but could
> > > refcount_inc_not_zero() fail for bhash2 under spin_lock_bh() ?
> > 
> > My understanding is that it can't fail, but I prefered to keep the test
> > to be on the safe side.
> > 
> > I can post a v3 using a plain sock_hold(), if you prefer.
> 
> I prefer sock_hold() because refcount_inc_not_zero() implies that it could
> fail and is confusing if it never fails.

Ok, I'll do that for v3.